content: /*
   * Copyright (C) 2007 Esmertec AG.
   * Copyright (C) 2007 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package spam.blocker.util.pdu.pdu;
  
  
  import java.io.ByteArrayOutputStream;
  
  public class QuotedPrintable {
      private static byte ESCAPE_CHAR = '=';
  
      /**
       * Decodes an array quoted-printable characters into an array of original bytes.
       * Escaped characters are converted back to their original representation.
       *
       * <p>
       * This function implements a subset of
       * quoted-printable encoding specification (rule #1 and rule #2)
       * as defined in RFC 1521.
       * </p>
       *
       * @param bytes array of quoted-printable characters
       * @return array of original bytes,
       *         null if quoted-printable decoding is unsuccessful.
       */
      public static final byte[] decodeQuotedPrintable(byte[] bytes) {
          if (bytes == null) {
              return null;
          }
          ByteArrayOutputStream buffer = new ByteArrayOutputStream();
          for (int i = 0; i < bytes.length; i++) {
              int b = bytes[i];
              if (b == ESCAPE_CHAR) {
                  try {
                      if('\r' == (char)bytes[i + 1] &&
                              '\n' == (char)bytes[i + 2]) {
                          i += 2;
                          continue;
                      }
                      int u = Character.digit((char) bytes[++i], 16);
                      int l = Character.digit((char) bytes[++i], 16);
                      if (u == -1 || l == -1) {
                          return null;
                      }
                      buffer.write((char) ((u << 4) + l));
                  } catch (ArrayIndexOutOfBoundsException e) {
                      return null;
                  }
              } else {
                  buffer.write(b);
              }
          }
          return buffer.toByteArray();
      }
  }
  